The present invention relates to surveillance satellites and, in particular, it concerns a low orbit missile-shaped satellite for electro-optical earth surveillance and other missions.
Earth surveillance satellites are usually designed to stay in high enough orbits (typically 350-800 km), where the residual atmospheric drag is negligible. Their specific shape and their cross section are therefore of no significant importance. These relatively high altitude orbits impose relatively large aperture optics to achieve a required ground resolution, resulting in satellite weight of several hundreds of kilograms. Changing a satellite orientation is a relatively slow process based on conservation of momentum using reaction wheels. As a result, these satellites are limited in term of observing several regions of interest during limited time interval. These satellites are usually designed to stay in orbit for several years, requiring very high reliability. Moreover, the satellite must be highly economical on expendable resources such as fuel.
In the past, surveillance satellites were launched to low orbits (˜200 km) in order to achieve high resolution. These satellites were very big (their weight was several tons) since they required a lot of fuel to overcome the atmospheric drag.
For the two cases described above the launch is very expensive and the ‘cost per image’ is very high.
Therefore, there is a need for satellite which is relatively inexpensive, can be launched using low cost boosters and can make large number of observations in a short time.